Back-arc dynamics controlled by slab rollback and tearing: a reappraisal of seafloor spreading and kinematic evolution of the Eastern Algerian basin (western Mediterranean) in Middle-Late Miocene

Abstract

In spite of clear fan-shaped magnetic anomalies in the Eastern Algerian Basin (EAB), the way how and the time when seafloor spreading occurred are still debated. In this work, a new seismo-stratigraphic interpretation based on deep-penetration reflection seismic data correlated to reduced-to-the-pole magnetic anomalies and to onshore-offshore litho-stratigraphic correlation of Pre-Messinian units bring new constraints on its age and mode of opening. Our results reveal that the seafloor spreading of EAB occurred with a intermediate to fast half-spreading rate of 3.7±0.5 cm/yr during 2.45±0.18 Myr in Langhian-Serravalian times, i.e. after the Corsica-Sardinia block rotation and the collision of Lesser Kabylia with Africa. We revise the kinematics of the Algero-Balearic domain into three stages: (1) birth of a highly stretched continental basin accommodating the southern drift of the Kabylies driven by Tethyan slab rollback between ˜23 and ˜15 Ma, (2) fast opening of a new basin (EAB) between 15.2 and 12.7 Ma by clockwise rotation of a Greater Alboran Block (GALB), and (3) continuation of westward translation of the GALB. The last stages match both the late formation of Subduction-Transform Edge Propagator (STEP) faults at the toes of the Algero-Balearic margins and the post-collisional volcanic migration along the Algerian margin interpreted as related to slab break-off. This new scheme invalidates most previous opening models of the Algero-Balearic basin and favors a significant stretching and splitting of the GALB into several continental fragments resulting from the westward propagation of the arcuate subduction front by lateral tearing of a narrow slab.

Two Cenozoic Extensional Phases in Mallorca and Their Bearing on the Geodynamic Evolution of the Western Mediterranean

“…At present, the lithospheric features of Mallorca hardly fit earlier tectonic models for the island, evoking Early Miocene NW-directed crustal thickening followed by only minor SE-directed extension in the Middle to Late Miocene (e.g., Gelabert, 1998;Sabat et al, 2011). Middle Miocene SW-directed extension in Mallorca is, however, compatible with some models proposed for the opening of the Algero-Balearic basin to the SE (e.g., Booth-Rea et al, 2007;de la Peña, Ranero, et al, 2020;Haidar et al, 2021;Mauffret et al, 2004).…”

“…This hypothesis contrasts with models suggesting very minor displacements-below 200, or even 100 km-for the Betic hinterland with respect to Iberia (e.g., Frasca et al, 2015;Pedrera et al, 2020;Vergés & Fernàndez, 2012). Still, we believe that the geodynamic evolution proposed here would explain the great diversity of available geological and geophysical data presented for the geological setting: sediment provenance (Bourrouihl, 1983;Cohen, 1980;Donoso et al, 1982;Hollister, 1942;Moragues et al, 2018;Pomar & Rodríguez-Perea, 1983), detrital zircon population ages (Jabaloy-Sánchez et al, 2021), subducted slab bodies (e.g., Bezada et al, 2013;Faccenna et al, 2014;Fichtner & Villaseñor, 2015), tectonic evolution (this work and references therein), Algero-Balearic basin development (e.g., Booth-Rea et al, 2007;de la Peña, Ranero, et al, 2020;Haidar et al, 2021;Mauffret et al, 2004), fossil faunal dispersal (e.g., Martín-Suarez et al, 2012;Suarez et al, 1993), and the extensional collapse of the Mallorca and Betic FTB as discussed in this work. We do hold that some of these data, for example, sediment provenance analysis in the Mallorca basins, calls for future work using updated heavy mineral dating and analysis methods.…”

“…These faults would form part of a wide STEP zone, together with other parallel dextral ones that crop out onshore in the Southeastern Betics, such as the Crevillente, Alpujarras, Torcal, and the Orient fault in Mallorca. This system of transform faults, together with a symmetrical STEP fault system along the North‐Maghrebian margin, probably contributed to the west‐south westward stretching and displacement of the Alboran Domain during the Middle to Late Miocene (e.g., Giaconia et al., 2014; Haidar et al., 2021; Hidas et al., 2019; Mancilla et al., 2015; Medaouri et al., 2014; Pérez‐Valera et al., 2013).…”

“…The Liguro‐Provencal basin formed behind the Oligocene to Early Miocene volcanic arc, built mostly along western Sardinia in relation to earlier stages of Calabrian slab subduction (e.g., Faccenna et al., 2001). The Algero‐Balearic basin shows a more complex evolution, presenting segments of different ages, as made manifest by the heat flow and magnetic anomaly distribution, suggesting younger oceanic crust located at the western and eastern ends of the basin (Haidar et al., 2021; Poort et al., 2020). Moreover, the Algero‐Balearic basin is underlain by at least two different Tethyan slab segments, underneath the Betics‐Rif and Algerian‐Tunisian orogenic arcs (e.g., Faccenna et al., 2014; Fichtner & Villaseñor, 2015; Kumar et al., 2020; van Hinsbergen et al., 2014).…”

“…Differential amounts of Tertiary extension between these domains were accommodated along NW-SE directed transfer fault zones such as the North Balearic and Central fracture zones, among others, in a process accompanied by important Early to Middle Miocene magmatism (Maillard et al, 2020;Pellen et al, 2016; Figure 1). The role of Oligocene to Early Miocene extension in the formation of the present Algero-Balearic basin to the South has also been questioned; for this region several authors have highlighted the importance of oceanic crust development during the Middle to Late Miocene (Booth-Rea et al, 2007;Booth-Rea, Ranero, & Grevemeyer, 2018;de la Peña, Grevemeyer, et al, 2020;de la Peña, Ranero, et al, 2020;Haidar et al, 2021;Jolivet et al, 2006;Mauffret et al, 2004). This process followed the westward retreat of the Gibraltar arc subduction system (Lonergan & White, 1997) and concomitant slab detachment or tearing along its Betic and Rif-Tell orogenic limbs, respectively (e.g., Duggen et al, 2003;García-Castellanos & Villaseñor, 2011;Hidas et al, 2016Hidas et al, , 2019Mancilla et al, 2015).…”